1. Field of the Invention
The present invention relates generally to single two-fiber optical channel shared protection rings, and particularly to protection switching in single two-fiber optical channel shared protection rings.
2. Technical Background
Optical protection ring topologies are currently being deployed by network providers because of their cost savings, survivability, and ability to self-heal. Ring topologies typically include a plurality of client access nodes that are interconnected by at least two optical fibers to form a ring. Traffic is transmitted from node to node around the ring. Wavelength Add/Drop multiplexers (WADMs) are employed at each node to allow clients to gain access to the ring. Client transmitters are coupled to the add portion of the WADM to insert client traffic onto the ring, whereas client receivers are coupled to the drop portion of the WADM to receive ring traffic.
Optical protection rings can survive and self-heal from ring fault conditions by providing duplicate and geographically diverse paths for all of the client traffic propagating on the ring. In a two-fiber ring, this is accomplished by providing two fibers that carry traffic in opposite directions. In addition, each fiber reserves approximately half of its bandwidth 30 for protection purposes. Thus, if a cable is cut between two nodes, or a wavelength channel transmitter becomes disabled at a particular node, or if there is a switch fabric failure, the ring will detect the fault condition, and route traffic around the damaged network component using the reserved protection bandwidth until a repair can be effected.
The protection switching used to implement the self-healing features of the ring is resident in each node. However, conventional protection switches have several shortcomings.
First, most protection switches are not versatile enough to provide protection for both multi-channel failures and single channel failures. Second, most protection switches employ large switching fabrics. Thus, if the switching fabric itself experiences a failure, a single point failure severely impacting the operation of the entire ring may result. Thus, what is needed is a protection switch that includes small modular switching fabrics to substantially reduce the possibility of single-point failures. Further, a protection switch is needed that will provide protection for both multi-channel failures and single channel failures.
The present invention includes a protection switch having a plurality of small modular switching fabrics that substantially reduce the possibility of single-point failures. Each modular switch fabric can be easily replaced without affecting other operational portions of the protection switch. The protection switch of the present invention provides protection for both multi-channel failures and single channel failures.
One aspect of the present invention is a protection switch in a node of a two-fiber optical channel shared protection ring. The node includes a plurality of primary clients and a plurality of pre-emptible clients. Each fiber in the two-fiber optical channel shared protection ring propagates at least one working wavelength channel dedicated to primary client traffic and at least one protection wavelength channel which may accommodate extra client traffic. The protection switch includes an optical signal monitor coupled to the two-fiber optical channel shared protection ring. The optical signal monitor is operative to detect multi-wavelength channel failures and single wavelength channel failures in the two-fiber optical channel shared protection ring. An electrical switching circuit is coupled to the optical signal monitor. The electrical switching circuit includes a plurality of modular switching fabrics. Each modular switching fabric of the plurality of modular switching fabrics includes a ring switch mode that is responsive to the multi-wavelength channel failures, and a span switch mode that is responsive to the single wavelength channel failures.
In another aspect, the present invention includes a modular switching fabric for use in a protection switch resident in a node of a two-fiber optical channel shared protection ring. Each node includes a plurality of primary clients and a plurality of pre-emptible clients. Each fiber of the two fibers propagates at least one working wavelength channel dedicated to primary client traffic and at least one protection wavelength channel which may accommodate extra client traffic. The protection switch includes a first 3xc3x971 switch coupled to a first primary client receiver. A first 2xc3x971 switch is coupled to a first extra client receiver.
A second 3xc3x971 switch is coupled to a second primary client receiver. A second 2xc3x971 switch is coupled to a second extra client receiver. A controller is coupled to the first 3xc3x971 switch, the second 3xc3x971 switch, the first 2xc3x971 switch, and the second 2xc3x971 switch. The controller is operative to actuate the switches in order to receive the primary client""s receive signal from a protection wavelength propagating on the first fiber instead of a working wavelength channel propagating on the second fiber, and pre-empt extra client traffic, in response to a multi-wavelength channel failure.
In yet another aspect, the present invention includes a two-fiber optical channel shared protection ring for bi-directional communications between a plurality of nodes. Each node includes a plurality of primary clients and a plurality of pre-emptible clients. Each fiber of the two fibers propagates at least one working wavelength channel dedicated to primary client traffic and at least one protection wavelength channel which may accommodate extra client traffic. The protection switch includes a first 3xc3x971 switch having inputs coupled to a first primary client transmitter, a first extra client transmitter, and a second primary client transmitter. A first 2xc3x971 switch has an input coupled to the first extra client transmitter and an output connected to the first 3xc3x971 switch. A second 3xc3x971 switch has inputs coupled to a first primary client transmitter, a second extra client transmitter, and a second primary client transmitter. A second 2xc3x971 switch has an input coupled to the second extra client transmitter and an output connected to the second 3xc3x971 switch. A controller is coupled to the first 3xc3x971 switch, the second 3xc3x971 switch, the first 2xc3x971 switch, and the second 2xc3x971 switch. The controller is operative to actuate the switches in order to switch a primary client""s transmission signal from a working wavelength propagating on a first fiber of the two fibers to a protection wavelength propagating on a second fiber of the two fibers in response to a multi-wavelength channel failure.
In yet another aspect, the present invention includes a method for switching bi-directional traffic between a plurality of nodes in a two-fiber optical channel shared protection ring. Each node includes a plurality of primary clients and a plurality of pre-emptible clients. Each fiber of the two fibers propagates at least one working wavelength channel dedicated to primary client traffic and at least one protection wavelength channel which may accommodate extra client traffic. The method includes providing a protection switch in each node of the plurality of nodes. Each protection switch is coupled to the two fibers, the plurality of primary clients, and the plurality of pre-emptible clients. The protection switch includes a plurality of modular switching fabrics. A fault condition is detected in the two-fiber optical channel shared protection ring. At least one of the modular switching fabrics is actuated in response to the step of detecting, whereby a primary client""s transmission signal is switched from a working wavelength propagating on a first fiber of the two fibers to a protection wavelength propagating on a second fiber of the two fibers. The primary client""s receive signal is switched from a working wavelength propagating on the second fiber to a protection wavelength propagating on the first fiber. Extra client traffic is preempted.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.